Semifluorinated Chains at the Air/Water Interface:  Studies of the Interaction of a Semifluorinated Alkane with Fluorinated Alcohols in Mixed Langmuir Monolayers

Abstract

Mixtures of a semifluorinated alkane 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-henicosafluorotriacontane (abbr. F10H20) and different alcohols were investigated at the air/water interface using surface pressure-area isotherms complemented with BAM images. In our studies, octadecanol and its fluorinated derivatives differing in the degree of fluorination were researched. To verify the influence of an iso branching of the fluorinated segment in an alcohol molecule, the properties of perfluorooctyldecanol and perfluoro-iso-nonyldecanol in mixtures with F10H20 were compared. From the isotherms datapoints, the excess of free energy of mixing (DeltaG(exc)) together with the interaction parameter (alpha) were calculated. On the basis of the additivity rule and BAM images, phase diagrams for all of the investigated systems were constructed. It occurs that F10H20 mixes with the fully hydrogenated alcohol, octadecanol, within the whole range of alcohol mole fractions, whereas it is completely immiscible with its perfluorinated analogue. Regarding the mixtures of F10H20 with semifluorinated alcohols, it turned out that these systems exhibit limited miscibility, i.e., are miscible at a low semifluorinated alcohol proportion, whereas upon increasing alcohol content, the systems start to demix. It may be concluded that the molecular packing in mixed monolayers is the key factor determining the miscibility of F10H20 of the investigated alcohols.

Thermodynamic Behaviour of Mixed Films of an Unsaturated and a Saturated Polar Lipid. (Oleic Acid-Stearic Acid and POPC-DPPC)

“…Seoane et al [34] reported mixed films of cholesterol with saturated or unsaturated fatty acids, but these are not discussed here due to the peculiar characteristics of cholesterol. Several authors [23,[25][26][27]30,32] have also observed phase separation in fatty acid mixed monolayers of fluorinated and hydrogenated amphiphiles.…”

“…One of the main aspects of these mixtures is the miscibility and phase separation. Recent articles on mixed fatty acids systems are those of [23][24][25][26][27][28][29][30][31][32]. Furthermore, since fatty acids or phospholipids usually present unsaturations in the hydrocarbon chains, the study of mixtures of saturated and unsaturated compounds is of interest.…”

Thermodynamic and elastic fluctuation analysis of langmuir mixed monolayers composed by dehydrocholic acid (HDHC) and didodecyldimethylammonium bromide (DDAB)

“…The net interaction between two components in a mixed monolayer, at a constant surface pressure and absolute temperature T, can be evaluated from the calculation of excess Gibbs energy ( G E mix ) and the interaction parameter (˛) [12,13,16,19], which are given by:…”

“…Since the values of the first virial coefficient (b 0 ) were lower than 1 for all studied systems, two-dimensional molecular aggregates existed at low pressures. Thus their aggregation number (1/b 0 ) could be estimated [19], see Table 4. This could be indirectly related to the existence of laterally structured microdomains.…”

Langmuir Monolayer Miscibility of Perfluorocarboxylic Acids with Biomembrane Constituents at the Air-Water Interface

“…The ΔV-A isotherms of FnCOOH monolayers indicate changes in molecular orientation upon compression; similarly, the ΔV value of hydrogenated lipid monolayers indicates positive variation in molecular orientation upon compression. However, the isotherms of the F-chains have an sign opposite to those of hydrogenated lipid monolayers or exhibit negative variation due to the electronegativity as the molecular areas decrease, which has been thoroughly discussed 16,32,34,35,37,40,69 . Recently, it has been reported that the monolayers of ethers having a long-chain hydrocarbon and a fluorinated headgroup exhibit large negative ΔV values 70 72 .…”